A new thick film humidity sensor has been developed which consists of a interdigitated capacitor coated with an ink glass. A sensitive layer of hydrocerussite is produced by submerging the device in deionized water. The crystal growth is analyzed and sensor measurements have been carried out on the humidity, temperature and hysteresis characteristics. It is concluded from the results that the sensor has a good sensitivity, low temperature dependence and simplicity of manufacture. In particular, the sensor with the Du Pont ink glass 5137 shows a very good response at low frequency.